Composite structures are desirable in many industries for many applications. For example, aircraft, space, and land/sea vehicles employ a variety of curved and multiple-contoured surface structures in their fabrication. Composite materials are commonly used for these structures because, among other desirable attributes, composite materials have high strength-to-weight ratios. Although composite materials possess high strength-to-weight ratios, the composite structures they are used to form are sometimes strengthened or stiffened using various types of stiffeners, such as ribs, spars, hats, or other structural members.
Stiffeners are attached to composite structures in many different manners. One such manner is by fastening with fasteners such as bolts or rivets. Since fasteners are typically inserted into holes, a drilling operation must be performed on the composite material. In addition, depending on the application for the composite structure, a countersink operation may have to be performed on the composite material.